The fine structure of microwave-induced magneto-oscillations in
photoconductivity of the two-dimensional electron system formed on a
liquid-helium surface
The influence of the inelastic nature of electron scattering by surface
excitations of liquid helium (ripplons) on the shape of magnetoconductivity
oscillations induced by resonance microwave (MW) excitation is theoretically
studied. The MW field provides a substantial filling of the first excited
surface subband which sparks off inter-subband electron scattering by ripplons.
This scattering is the origin of magneto-oscillations in the momentum
relaxation rate. The inelastic effect becomes important when the energy of a
ripplon involved compares with the collision broadening of Landau levels.
Usually, such a condition is realized only at sufficiently high magnetic
fields. On the contrary, the inelastic nature of inter-subband scattering is
shown to be more important in a lower magnetic field range because of the new
enhancement factor: the ratio of the inter-subband transition frequency to the
cyclotron frequency. This inelastic effect affects strongly the shape of
conductivity oscillations which acquires an additional wavy feature (a mixture
of splitting and inversion) in the vicinity of the level-matching points where
the above noted ratio is close to an integer.Comment: 10 pages 6 figure
